Santabarbaraite

Santabarbaraite is an amorphous ferric hydroxy phosphate mineral hydrate that was discovered in Tuscany, Italy during 2000. It also can be found in Victoria, Australia and Lake Baikal, Siberia. This phosphate mineral has a simplified formula Fe3+3(PO4)2(OH)3·5 H2O, which is the same formula of another non-amorphous phosphate mineral called allanpringite. Santabarbaraite occurs as pseudomorphic masses after vivianite (Fe3+2(PO4)2·8 H2O). In the process, monoclinic vivianite oxidizes to form the amorphous santabarbaraite. Pseudomorphism may be seen in Victoria, Australia, in Wannon Falls (originally a well-known locality for vivianite). It also may be seen at Lake Baikal, Siberia where the oxidized santabarbaraite may be seen as a rim surrounding vivianite due to exposure to air.